Liquid sealed suspension unit

ABSTRACT

A liquid sealed suspension unit includes a first member and a second member which are independent of each other and which are coupled together. A cylindrical rubber mount (43) is fastened to the first member, and the second member is mounted so as to be slidable in an axial direction thereof relative to the cylindrical rubber mount (43). The cylindrical rubber mount (43) has a plurality of rubber layers (46a, 46b, 46c) laminated via a plurality of cylindrical members (45a, 45b, 45c) such that they are different with respect to at least either of (i) thickness in their radial direction and (ii) height in their axial direction. A spring member (57), in the form of at least one spring coil, is interposed between a damper plate member (50) and an inner surface of a vessel (40) at the bottom of the vessel. This construction provides an increased displacement amplitude in the axial direction, and an excellent vibration absorptivity for both a roll and a pitch can be achieved.

TECHNICAL FIELD

The present invention relates to a liquid sealed type suspension unitand, more particularly, to a liquid sealed suspension unit that may beused in mounting a cab upon a body of an automobile such as anindustrial vehicle to effectuate its vibration absorption ability.

BACKGROUND ART

FIG. 1 of the drawings attached hereto shows the entire construction ofa part whereby a cab is mounted on a dump truck. A dump truck 1 has aframe 2 to which are fastened a pair of brackets 3 and 4 for supportinga floor 6 of a cab 5 via a pair of liquid sealed suspension units 10 and10. A said liquid sealed suspension unit 10 is effective to preventvibrations from a road and so forth from being transmitted directly tothe said cab 5.

FIG. 2 is a detailed view of a portion Π of FIG. 1. To the said bracket4 there is fastened a casing 11 of the said liquid sealed suspensionunit 10 by means of a bolt 12 and a nut 13. The said liquid sealedsuspension unit 10 has a guide shaft 14 that is fastened to the saidfloor 6 by means of a nut (or bolt) 15. Thus, the said cab 5 in a statein which vibrations may be absorbed by means of the said liquid sealedsuspension 10 is mounted on the said bracket 4.

As a said liquid sealed suspension unit 10 of this sort whicheffectuates a vibration absorption requirement there have hitherto beknown what are shown in FIGS. 3 and 4.

In what is shown in FIG. 3, the said guide shaft 14 having a bolt 16 iscoupled to the said casing 11 via a cylindrical rubber mount 17. Thesaid casing 11 has one end fastened to a vessel 20, that is formedtherein with a liquid sealed chamber 29 in which a damping liquid 21 issealed. The said liquid sealed chamber 29 contains a damper plate member23 with a rubber stopper 24, which is fastened to the downward end ofthe said guide shaft 14 by means of a bolt 22. The said damper platemember 23 is formed with a bore 25 whereas the said vessel 20 is formedwith an inlet port 26.

The said damping liquid 21 is injected or poured into the said liquidsealed chamber 29 through the inlet port 26 of the said vessel 20, andthe bore 25 in the said damper plate member 23 is used to inject or pourthe said damping liquid 21 into an upper cavity of the said damper platemember 23.

And, if a vertical (axial) vibratory load is applied to the said guideshaft 14, the said damper plate member 23 acts to agitate the dampingliquid 21 so that the vibrations may be damped with a damping force thatis then generated.

Also, in what is shown in FIG. 4, a casing 30 is coupled with a guideshaft 31 having a bolt 16 via a cylindrical rubber mount 33 thatconsists of cylindrical rubber sections of an identical thicknesslaminated with intervening cylindrical plate members 32. The said guideshaft 31 has a whirl-stop pin 34 that is effective, when the said bolt16 is fastened, to prevent the said guide shaft 31 itself from beingturned. A downward end of the said casing 30 and a stopper plate 36 hasfastened thereto a vessel 35 in which a said liquid sealed chamber 29containing a said damping liquid 21 is formed. The said liquid sealedchamber 29 also contains a said damper plate member 23 fastened to thedownward end of the said guide shaft 31 by means of a said bolt 22 aswell as the said stopper plate 36. The said damper plate member 23 has arubber stopper 37 fastened to its upper surface and a foamed elasticbody 38 securely sandwiched between its lower surface and a plate 39.

Of the above mentioned constructions which have been adopted in theprior art, what is shown in FIG. 3 has the problem that the said damperplate 23, due to its circular configuration, has only been effective togenerate a damping force in its axial direction. However, the saidrubber mount 17 which is designed to produce a vibration absorbingaction both in its axial and transverse directions has, due to itstransverse rubber stiffness that is lower than its vertical rubberstiffness because of its unitary structure with a large thickness,allows vibrations with a complicated orientation to be set free in thetransverse direction, and hence a cause to generate a rolling from sideto side.

On the other hand, what is shown in FIG. 4 and has been adopted also inthe prior art is characterized by a construction in which the saidrubber mount 33, due to its laminated structure, has had its transversespring constant that is higher than that in what is shown in FIG. 3 andits axial spring constant that is reasonably high as well. However, withsuch a construction, the displacement component attainable in the axialdirection, rather than the radial rubber distortion constant related tothe rubber durability, remains within the order of ±6 mm and cannot belargely taken. Therefore, this has the problem that a vehicle therewithis not comfortable to ride in and its vibration absorptivity is thuspoor in spite of the fact that there may not be a roll due to atransverse vibratory component since the transverse spring constant islarge (stiffness is high) because of a laminated structure of rubbersections which are of an identical thickness.

The present invention has taken account of the above mentioned problemsin the prior art and has for its object to provide a liquid sealedsuspension unit whereby a vehicle therewith becomes comfortable to ridein owing to the fact that an increased vibratory amplitude can be takenin the axial direction and the rubber durability that is related to thesaid increased vibratory amplitude and hence the damping effect can bemarkedly enhanced, and an excellent vibration absorbing effect as awhole can be obtained owing to the fact that there can be no roll due tovibrations in complicated directions because of both the transversedamping action and the small amplitude vibration absorbing action whichcan be enhanced.

SUMMARY OF THE INVENTION

In order to achieve the object mentioned above, there is provided inaccordance with the present invention, in a first general form ofembodiment thereof, a liquid sealed suspension unit in which: a firstmember and a second member which are independent of each other arecoupled together via a cylindrical rubber mount; and a damping liquid issealed in, and a damper plate member that is provided at one end of thesaid second member is contained within, a liquid sealed chamber formedin a vessel that is fastened to the said first member,

characterized in that:

the said cylindrical rubber mount is fastened to the said first memberwhereas the said second member is fitted so as to be slidable in anaxial direction thereof relative to the said rubber mount; the saidcylindrical rubber mount is constituted by a plurality of cylindricalrubber layers laminated via a plurality of cylindrical members so thatthey may be different with respect to at least either of thickness intheir radial direction and height in their axial direction; and a springmember comprised of at least one spring coil is interposed between thesaid damper plate member and an inner surface of the said vessel at itsbottom.

According to the construction mentioned above, it can be seen that whenrelative to the said first member the said second member is vibrated inits axial direction towards the said liquid sealed chamber, thevibrations of the said second member will be resiliently supported bythe said spring member comprised of the said at least one coil spring.

Also, when relative to the said first member the said second member istransversely vibrated, it can be seen that the said transversevibrations will be resiliently supported by an elastic force of the saidlaminated rubber layers inside of the said rubber mount and, if the saidtransverse vibrations are large, will be resiliently supported as thesaid rubber mount as a whole is deformed in its radial direction.

And, according to this construction, it can be seen that since the axialsupport is performed with the said spring member comprised of the saidat least one spring coil, an increased vibratory amplitude will beobtained in the axial direction. Also, by permitting the transversesupport to be performed with the said cylindrical rubber mount that isconstituted by the said plurality of cylindrical rubber layers which aredifferent with respect to the thickness in their radial direction andthe height in their axial direction, it can be seen that since for sucha transverse force a small amplitude vibration can be met with a lowspring constant (i. e. with a soft spring property) and a largeamplitude vibration can be met with a high spring constant (i. e. with ahard spring property), absorbing the transverse vibrations andpreventing a rolling from side to side will both be achieved.

Also, in the said cylindrical rubber mount, the cylindrical rubberlayers in the said radial direction may be different in hardness.

According to this arrangement, by, for example, rendering a saidcylindrical rubber layer inner in the said radial direction of a loweredhardness and a said cylindrical rubber layer outer in the said radialdirection of a higher hardness, it can be seen that absorbing transversevibrations in a small amplitude range and preventing a roll from side toside in a large amplitude range will both be achieved.

Also, in the said cylindrical rubber mount, at least one of the saidcylindrical rubber layers has a cross sectional configuration in whichits outer side is higher than its inner side in the said axialdirection.

According to this construction, it can be seen that the transversespring property will be rendered non-linear and smoothly solid.

More specifically, since for transverse vibrations a small amplitudevibration can be met with a soft spring property and a large amplitudevibration can be met with hard spring property, it can be seen thatabsorbing the transverse vibrations smoothly and preventing a roll fromside to side will both be achieved.

Further, a said cylindrical member that is located at the inner side ofthe said cylindrical rubber mount may have a height that is equal tosuch height that a member that is coupled to the other side of the saidsecond member, makes a contact with the upper end of the saidcylindrical member when the said second member is displaced towards thebottom inner surface of the said vessel.

According to this construction, it can be seen that since a load that isapplied after the upper end of the said cylindrical member makes acontact with the said second member can be supported by a force ofdeformation in a shearing direction of the said rubber mount as well asthe said spring member and any vibration can then be supportedresiliently by both the laminated rubber layers of the said rubber mountand the said at least one coil spring, the absorptivity for a largeamplitude vibration and the strength of vibration absorption will bothbe enhanced.

Further, there may be provided a roll preventing stopper at outside of asleeve which retains a bearing that is fitted so as to be axiallyslidable relative to the said second member and to which the saidcylindrical rubber mount is fastened so that the said roll preventingstopper may be bought into a loosely fitting state with an innercircumferential surface of a said inner cylindrical member therein thatis opposing to the said sleeve substantially across an inner side rubberlayer.

According to this construction, it will be seen that with the said rollpreventing stopper coming into contact with the said innercircumferential surface of a said inner cylindrical member, an excessiveroll from side to side can be prevented.

Further, there may be provided a shield member for covering an upperportion of the said cylindrical rubber mount and a sliding portionbetween the said cylindrical rubber mount and the said second memberfrom an above side.

According to this construction, it will be seen that since at least theupper part of the said cylindrical rubber layers of the said cylindricalrubber mount and the said sliding portion as a whole is shielded fromthe outside, the intrusion of foreign matters such as earth and sand,dust and water into these parts and portions can be prevented.

In order to achieve the object mentioned above, there is also providedin accordance with the present invention, in a second general form ofembodiment thereof, a liquid sealed suspension unit in which: a firstmember and a second member which are independent of each other arecoupled together via a cylindrical rubber mount; and a damping liquid issealed in, and a damper plate member that is provided at one end of thesaid second member is contained within, a liquid sealed chamber formedin a vessel that is fastened to the said first member,

characterized in that:

the said cylindrical rubber mount is fastened to the said first memberwhereas the said second member is fitted so as to be slidable in anaxial direction thereof relative to the said rubber mount; the saidcylindrical rubber mount is constituted by a plurality of cylindricalrubber layers laminated via a plurality of cylindrical members so thatthey may be different with respect to at least either of thickness intheir radial direction and height in their axial direction; a damperreceiving member is contained in the said liquid sealed chamber so as tobe slidable along an inner surface of the said vessel at its bottomwhereas the said damper receiving member and the said damper platemember are fitted with each other so as to be slidable in an axialdirection relative to each other; and a spring member comprised of atleast one spring coil is interposed between the said damper receivingmember and the said damper plate member.

According to this construction, it can be seen that when an impact forceof a large amplitude in the transverse direction is acting, the saiddamper plate member and the said damper receiving member will be causedto slide with each other along a bottom inner surface of the said vesseland a sliding frictional force that is then generated acts toeffectively damp the above mentioned large impact force.

And, one of the said damper plate member and the said damper receivingmember may be formed with a guide bore and the other of the said damperplate member and the said damper receiving member may be provided with aguide rod which is slidably fitted in the said guide bore with adiametrical interstice between them such that the said damping liquidcan freely be passed therethrough.

According to this construction, it can be seen that since an intersticeis formed at an interface at which the said guide bore and the saidguide rod are fitted with each other and, when the said damp platemember is sliding in its axial direction, the said damping liquidintroduced into the said guide bore is allowed to flow freely throughthe said interstice, and any damping resistance by the said dampingliquid will be eliminated.

Moreover, according to this construction, when a transverse force isacting to vibrate the said guide shaft transversely with a smallamplitude that corresponds to a backlash between the said guide bore andthe said guide rod, it can be seen that the said damper receiving memberwill not be displaced transversely. Also, when a force of a largeamplitude that exceeds the said backlash is acting, it can be seen thatthe said damper receiving member will be displaced transversely togenerate between the said damper receiving member and the said vessel asliding frictional force with which a frictional damping force is actingwhereby a large damping force will be developed.

Accordingly, this will enable a vehicle to be comfortable to ride inwhere a high frequency vibration with a small transverse amplitudedevelops as in the case in which the vehicle is traveling for thepurpose of leveling the land for construction as on the graveled ground.

Also, one of the said damper plate member and the said damper receivingmember may be formed with a guide bore whereas the other of the saiddamper plate member and the said damper receiving member may be providedwith a guide rod which is slidably fitted without a backlash in the saidguide bore; one of the said guide bore and the said guide rod may have across sectional configuration which is different from that of the otherof them so that an interstice may be formed between an inner surface ofsaid the guide bore and an outer surface of the said guide rod such thatthe said damping liquid can freely be passed therethrough.

According to this construction, it can be seen that when a transverseforce is acting, then since the said damper plate member and the damperreceiving member as a whole are vibrated transversely, a good responsewill be obtainable to enable the vehicle to be comfortable to ride inwhen traveling on a not so much heavily bad land.

Further, the said damping plate member has its peripheral surface whichis formed with a downward tapered surface and an upward tapered surface;the said downward tapered surface is opposing to an inner surface of thesaid vessel; and the said upward tapered surface is opposing to an innersurface of a stopper member disposed above the said vessel.

According to this construction, for the vertical vibrations of the saiddamper plate member it is possible to generate a small damping force ifthe amplitude is small and to generate a large damping force if theamplitude is large.

Further, said spring member may comprise a plurality of coil springs.

According to this construction, it is possible to set up the springproperty to be rigid in the load range of a mounting load, and to besoft in the load range of a vibration absorbing region that exceeds thismounting load. It is also possible to reduce the amount of displacementin accordance with a difference between mounting loads to reduce adeviation of the said amount of displacement while maintaining anexcellent vibration absorptivity.

Further, if the said damping liquid may comprise a silicone oil havingincorporated therein an additive agent with a lubricity, such as nylon(trade name), polyacetal or polystyrene, the wear of constituent membersof the present liquid sealed suspension unit by the damping liquid thatis vibrated by the vibrations of the said damper plate member can besubstantially reduced.

In order to achieve the object mentioned previously, there is alsoprovided in accordance with the present invention, in a third generalform of embodiment thereof, a liquid sealed suspension unit in which: afirst member and a second member which are independent of each other arecoupled together via a cylindrical rubber mount; and a damping liquid issealed in, and a damper plate member that is provided between one end ofthe said second member and an inner surface of a vessel at its bottom iscontained within, a liquid sealed chamber formed in the said vessel thatis fastened to the said first member,

characterized in that:

the said cylindrical rubber mount is fastened to the said first memberwhereas the said second member is fitted so as to be slidable in anaxial direction thereof relative to the said rubber mount; the saidcylindrical rubber mount is constituted by a plurality of cylindricalrubber layers laminated via a plurality of cylindrical members so thatthey may be different with respect to at least either of thickness intheir radial direction and height in their axial direction; a damperreceiving member is contained in the said liquid sealed chamber so as tobe slidable along the bottom inner surface of the said vessel; the saiddamper receiving member and the said damper plate member are fitted witheach other so as to be slidable relative to each other in an axialdirection; a stopper is provided in the said vessel for regulating adisplacement of the said damper plate member towards a side of the saidsecond member; and a first and a second spring coil constituting aspring member are interposed between the said damper receiving memberand the said damper plate member and between the said damper platemember and the said second member, respectively, so that in a state inwhich the said damper plate member does not make a contact with the saidstopper, both of the said first and second coil springs may be effectiveand that in a state in which the said damper plate member makes acontact with the said stopper, only the said second spring may beeffective.

In order to achieve the object mentioned previously, there is alsoprovided in accordance with the present invention, in a fourth generalform of embodiment thereof, a liquid sealed suspension unit in which: afirst member and a second member which are independent of each other arecoupled together via a cylindrical rubber mount; and a damping liquid issealed in, and a damper plate member that is provided at one end of thesaid second member is contained within, a liquid sealed chamber formedin a vessel that is fastened to said first member,

characterized in that:

the said cylindrical rubber mount is fastened to the said first memberwhereas the said second member is fitted so as to be slidable in anaxial direction thereof relative to the said rubber mount; the saidcylindrical rubber mount is constituted by a plurality of cylindricalrubber layers laminated via a plurality of cylindrical members so thatthey may be different with respect to at least either of thickness intheir radial direction and height in their axial direction; a damperreceiving member is contained in the said liquid sealed chamber so as tobe slidable along a bottom inner surface of the said vessel; and a firstand a second spring coil constituting a spring member are interposedbetween the said damper receiving member and the said damper platemember and between the said damper plate member and the said secondmember, respectively.

According to the above mentioned third and fourth general forms ofembodiment of the present invention, it is possible to set up the springproperty to be rigid in the load range of a mounting load and to be softin the load range of a vibration absorbing region that exceeds the saidmounting load. Since an increase in the amount of displacement due to adifference between mounting loads that occurs when the spring propertyis softened in order to enhance the vibration absorptivity is thereforenot produced in the load range of a cab mounting region, it will be seenthat a deviation in the said amount of displacement with a plurality ofliquid sealed suspension units in the said load range can be reduced.Thus, a deviation in the amount of displacement due to a differencebetween mounting loads that is created when the spring property issoftened in order to enhance an excellent vibration absorptivity can bereduced.

BRIEF EXPLANATION OF THE DRAWINGS

The present invention will better be understood from the followingdetailed description and the drawings attached hereto showing certainillustrative embodiments of the present invention. In this connection,it should be noted that such embodiments as illustrated in theaccompanying drawings are intended in no way to limit the presentinvention, but to facilitate an explanation and an understandingthereof.

In the accompanying drawings:

FIG. 1 is the entire constructive view of a cab mounting portion in adump truck;

FIG. 2 is a detailed view of a portion Π in FIG. 1;

FIG. 3 is a cross sectional view of an example in the prior art;

FIG. 4 is a cross sectional view of another example in the prior art;

FIG. 5 is a cross sectional view of a first embodiment of the liquidsealed suspension unit according to the present invention;

FIG. 6 is a cross sectional view showing the state in which a transverseload is acting in the above mentioned first embodiment of the presentinvention;

FIGS. 7A and 7B are each a cross sectional view showing the state inwhich an axial load is acting in the above mentioned first embodiment ofthe present invention;

FIG. 8A is a cross sectional view of a second embodiment of the liquidsealed suspension unit according to the present invention;

FIG. 8B is a cross sectional view showing the state in which atransverse load is acting in the above mentioned second embodiment ofthe present invention;

FIG. 9 is a cross sectional view showing a first example of a shieldingmember for covering the upper part of a cylindrical rubber mount in theabove mentioned second embodiment of the present invention;

FIG. 10 is a partial cross sectional view showing a second example of ashielding member for covering the upper part of a cylindrical rubbermount in the above mentioned second embodiment of the present invention;

FIG. 11 is a cross sectional view showing a further and third example ofa shielding member for covering the upper part of a cylindrical rubbermount in the above mentioned second embodiment of the present invention;

FIG. 12 is a cross sectional view showing a fourth example of ashielding member for covering the upper part of a cylindrical rubbermount in the above mentioned second embodiment of the present invention;

FIG. 13 is a cross sectional view of a third embodiment of the liquidsealed suspension unit according to the present invention;

FIGS. 14A and 14B are each a cross sectional view showing the state inwhich an axial load is acting in the above mentioned third embodiment ofthe present invention;

FIGS. 15A and 15B are each an explanatory view showing an operation inwhich a transverse load is acting in the above mentioned thirdembodiment of the present invention;

FIG. 16 is a cross sectional view showing another example of laminatedcylindrical rubber layers constituting a cylindrical rubber mount in theabove mentioned third embodiment of the present invention;

FIGS. 17A and 17B are each a cross sectional view showing a differentexample of the guide rod relative to a guide bore in the above mentionedthird embodiment of the present invention;

FIGS. 18A and 18B are cross sectional views of a forth and a fifthembodiment, respectively, of the liquid sealed suspension unit accordingto the present invention;

FIG. 19 is a graph showing the spring properties when an axial damper isoperated in the above mentioned third embodiment of the presentinvention;

FIG. 20 is a graph showing the spring property when a transverse damperis operated in the above mentioned third embodiment of the presentinvention;

FIG. 21 is a graph showing the spring property when a transverse damperin an example shown in FIGS. 12 and 16 is operated;

FIG. 22 is a graph showing the spring property in the above mentionedfourth embodiment of the present invention; and

FIG. 23 is a graph showing the spring property in the above mentionedfifth embodiment of the present invention.

BEST MODES FOR CARRYING OUT THE INVENTION

Hereinafter, suitable embodiments of the present invention with respectto a liquid sealed suspension unit will be set forth with reference tothe accompanying drawings hereof.

Firstly, an explanation will be given of a first embodiment of theliquid sealed suspension unit according to the present invention withreference to FIGS. 5 to 7.

A liquid sealed chamber 80 is configured as a space that is defined by atruncated conical vessel 40, a cylindrical rubber mount 43 and a rubberstopper 59. Various members for defining the said liquid sealed chamber80 are fastened to one another so as to be mutually integral. Inside ofthe said liquid sealed chamber 80 a damping liquid 60 as well as aspring member 57 comprised of a coil spring and a damper plate member 50that is integral with a guide shaft 42, is sealed. The said guide shaft42 is fitted so as to be axially slidable relative to the saidcylindrical rubber mount 43.

The said cylindrical rubber mount 43 is disposed outside of a sleeve 44that retains a bearing 70 in which the said guide shaft 42 is slidablyfitted, and is constituted by a plurality of cylindrical rubber layers46a, 46b, 46c and 46d laminated coaxially and circularly via a pluralityof cylindrical members 45a, 45b and 45c. The said laminated cylindricalrubber layers 46a, 46b, 46c and 46d are here different with respect tothickness in their radial direction and height in their axial direction.In their radial direction, their innermost layer 46a is the thickest andtheir outermost layer 46c is the thinnest so that they may beprogressively thickened towards their inside. In their axial direction,an inner of them is progressively lower than an outer of them.

The above mentioned laminated cylindrical rubber layers 46a, 46b, 46cand 46d are also adjusted with respect to their hardness so that onelocated outer may be harder than one located inner and that they may beprogressively hardened towards their outer side.

The said cylindrical rubber mount 43, together with a base plate 47provided with a rubber stopper 59, is fastened via the said cylindricalmember 45c that is located at the outermost position to a flange portion41 of the said vessel 40 by caulking or the like.

The said damper plate member 50, that is here cylindrical, is disposedin an area in which the said guide shaft 42 confronts with the saidliquid sealed chamber 80. And, the said cylindrical damper plate member50 is formed around its axis with a cylindrical recess of which theinside serves to receive the said spring member 57, thus constituting aspring reception portion 52. Also, the peripheral surface of the saiddamper plate member 50 is formed on its lower side with a downwardstapered surface 53 having the diameter progressively reduced downwardsand on its upper side with an upwards tapered surface 54 having thediameter progressively reduced upwards.

To the bottom surface of the said vessel 40 is fastened a springreception member 74 and between the latter and the said damper platemember 50 is interposed the said spring member 57 comprised of the coilspring, as shown.

On the other hand, the said rubber stopper 59, that is here againcylindrical and is formed with a tapered recess 59a, is disposed at thelower side of the said base plate 47 beneath the above mentionedcylindrical rubber mount 43. The said rubber stopper 59 is so taperedthat when the said damper plate 50 is moved upwards by a predetermineddistance or more, its upward tapered surface 54 may contact with theinner surface of the said recess 59a and may then no longer moveupwards.

The said damping liquid 60 is injected or poured through an inlet port(not shown) into the space within the above mentioned liquid sealedchamber 80 and is sealed therein. At this point it should be noted thatbetween the said guide shaft 42 and the said bearing 70 there areprovided seal members such as an O-ring 71 and a dust seal 72. The saidbearing 70 is composed of bearing units 70a and 70b into which it isdivided in its axial direction, the said bearing units 70a and 70b beingtightly contacted with each other to mutually close any interstice intheir axial direction.

Further, a liquid sealed suspension unit A as constructed as above toconstitute a first embodiment of the present invention has aconstruction in which the said guide shaft 42 having a whirl-stop pin 73is fastened by a bolt 81 to an attachment bracket 48 on the side ofmounting members such as a cab whereas the said flange portion 41 of thevessel 40 in which the said damping liquid 60 is sealed is supported ona bracket 61 on the main frame side.

In the construction mentioned above, the mounted member such as the cabis supported on the main frame side via the said liquid sealedsuspension unit A.

And, if the mounted member is then stationary, its weight will act as aninitial load on the said liquid sealed suspension unit A. This state isthe state shown in FIG. 5. The vertical load that is then produced havebeen supported by the said spring member 57 comprised of the coilspring.

Then, when the said mounted member is vertically vibrated, the saidguide shaft 42 will be caused to reciprocate in its axial direction, andthe vertical load that then develops will be supported resiliently bythe said spring member 57 whereas the resistance that develops when thesaid damper plate member 50 that is integral with the said guide shaft42 is reciprocated within the said damping liquid 60, will act as adamping force.

The damping force that is then produced by the reciprocating movement ofthe said damper plate member 50 within the said damping liquid willdepend upon the flow path length L₁ and the flow path spacing H₁ betweenthe downward tapered surface 53 of the said damper plate member 50 and aportion opposing thereto and the flow path length L₂ and the flow pathspacing H₂ between the upwards tapered surface 54 of the said dampingplate member 50 and a portion opposing thereto.

By means of the respective tapered surfaces 53 and 54 of the said damperplate member 50, a small damping force will develop for a smallvibration amplitude due to the above mentioned flow path spacings H₁ andH₂ which are large and an increased damping force will develop for anincreased vibration amplitude due to the above mentioned flow pathspacings H₁ and H₂ which are reduced. FIG. 7A shows an operating statewhen the said damper plate member 50 is moved downward (with theretracted part of a vibration) and FIG. 7B shows an operating state whenthe said damper plate member 50 is moved upwards (with the extended partof a vibration), each in the present embodiment of the invention. It canbe seen, however, that both of them show reduced flow path spacings H₁and H₂ as the vibration amplitude is increased as compared with the caseof FIG. 5 in which the case of a small vibration amplitude is shown.When the said damper plate member 50 is moved downwards as shown in FIG.7A, the lower surface of the said attachment bracket 48 on the side ofthe said mounted member will contact with the upper surface of thelaminated rubber layer 46d that is located at the outermost side of thesaid rubber mount 43, and will thus act as a stopper, thereby bringingabout a stroke end. Conversely, when the said damper plate member 50 ismoved upwards as shown in FIG. 7B, the upwards tapered surface 54 of thesaid damper plate member 50 will contact with the said rubber stopper 59and will thus act as a stopper, thereby bringing about another strokeend.

Also, when the said mounted body is transversely vibrated, the saidguide shaft 42 will be resiliently supported by the said rubber mount 43that is fastened to the said sleeve 44, via the said bearing 70 fittedtherewith and the said sleeve 44 for retention thereof. With the saidrubber mount 43 constructed in a laminated structure and beingstructurally softened towards its inside, the spring characteristicthereof will then exhibit a property that it becomes hardened (thespring constant increased) as the vibration amplitude is enlarged.

Further, when a rolling from side to side with a large amplitude isdeveloped, it should be noted as shown in FIG. 6 that the said guideshaft 42 will be largely inclined to displace the said damper platemember 50 while thrusting aside the said damping liquid 60 within thesaid liquid sealed chamber 80. Then, the said rolling will be damped bythe fluid resistance that is thereby produced.

Next, with reference to FIGS. 8A to 12, an explanation will be given ofa second embodiment of the liquid sealed suspension unit according tothe present invention.

Compared with the first embodiment previously set forth, the the liquidsealed suspension unit B shown in FIG. 8A additionally includes a coverplate 85 and a roll preventing stopper 49 and employs between the saiddamper plate member 50 and the said the inner bottom surface of the saidvessel 40 a said spring member 57 which is here comprised of a pluralityof coil springs.

FIG. 8A shows a state where the mounted member is stationary and itsweight will act as an initial load on the liquid sealed suspension unitB.

The said cover plate 85 serves to prevent dust, earth and sand, mud andso forth that may be piled upon a recess 86 above the said cylindricalrubber mount 43 from being intruded through interstices of the latter.On the other hand, the said roll preventing stopper 49, as shown in FIG.8B, is designed to contact with the innermost cylindrical member 45a,when the innermost, soft rubber layer 46a is deformed by a large rollfrom side to side of the mounted member to an extent that exceeds asmall amplitude which is effective to absorb vibrations, to prevent suchan excessive roll, and to serve to perform a stopper function bypermitting the said mounted body to be resiliently supported by theintermediate and outer laminated rubber layers 46b and 46c which arehigher in rubber hardness than the inner rubber layer 46a.

FIGS. 9 to 12 show a first to a fourth example of a cover plate member85 in this second embodiment of the present invention. The first exampleof the cover plate member shown in FIG. 9 has a skirt member 86 fastenedto its hem in such a manner that its lower end may come into an intimatecontact with the outer surface of the said rubber mount 43 so as to beslidable therewith. With the said lower end of the skirt member 86, theupper part of the said cylindrical rubber mount 43 is shielded.

In the second example shown in FIG. 10, a bellows rubber member 87 isdisposed above an inner portion of the said cylindrical rubber mount 43and is integrally formed with the latter and with the outermost 46d ofthe laminated cylindrical rubber layers, and its upper end is attachedto the inner central portion of a cover plate member 85 for covering theupper part of the cylindrical rubber mount 43.

In the second example shown in FIG. 11, a bellows rubber member 88 isattached at its lower end to a lower peripheral surface of the saidcylindrical rubber mount 43 and its upper end to the edge of a circularplate member 48a that is sandwiched between the top end of the saidguide shaft 42 and the said attachment bracket 48 as with the abovementioned cover plate member 85.

Further, as shown in FIG. 12, a flexure shield rubber member 89 may beused to bridge across the said plate member 48a and the hem portion ofthe said cylindrical rubber mount 43 for covering the latter as a whole.

By adopting any of these constructions, the entire upper portion of thesaid rubber mount 43 and its sliding portion are effectively shieldedfrom the outside to prevent any foreign matter such as dust, earth andsand, water or the like from being intruded into these portions.

The coil springs constituting the said spring member 57 in the abovementioned second embodiment are also used in a third embodiment of thepresent invention described later and hence an explanation of itsoperation is omitted here and will be given later in a description ofthe third embodiment which follows.

Now, an explanation will be given of the third embodiment of a liquidsealed suspension unit according to the present invention with referenceto FIG. 13.

In the present embodiment, a said vessel 40 has at its upper a saidflange portion 41 and, as a whole, is cup shaped with its inner bottomsurface being spherical. An axial upper side of the said guide shaft 42whose lower end meets with the inside of the said vessel 40 and which iscoaxially arranged with the latter is fitted with the said cylindricalrubber mount 43 so as to be slidable relative thereto.

The said cylindrical rubber mount 43 is composed of a plurality ofcylindrical rubber layers 46a, 46b, 46c and 46d laminated coaxially andcircularly via a plurality of cylindrical members 45a, 45b and 45c sothat the said rubber layers may be thinned progressively from theirinside towards their outside. In this connection it should be noted thatthe rubber layer 46d which is located at the outermost side, for thepurpose of acquiring a predetermined strength, is made thicker than theother rubber layers 46a, 46b and 46c. Of the above above mentionedcylindrical members 45a, 45b and 45c, the one that is located at thetheir innermost side is made higher than the others, thus extendingupwards so that when the said guide shaft 42 is moved downwards morethan a predetermined distance, the lower surface of the said bracket 48that is fastened to the said guide shaft 42 may contact with the upperend of the said cylindrical member 45a and the latter may thus serve asa stopper. Also, to the upper end portion of the said sleeve 44 there isfastened the said roll preventing stopper 49 made from a rubber and thatis variably spaceable from, and can make a roll preventing contact with,the inner surface of the said upwards extending cylindrical member 45a.

A said cylindrical damper plate member 50 is disposed in an area inwhich the lower end portion of the said guide shaft 42 meets with theinside of a said liquid sealed chamber 80. And, the said damper platemember 50 is formed around its axis with a bore 51 extending axially andthere is formed around the said bore 51 an annular recess which servesto receive the said spring member 57, thus constituting a springreception portion 52. Also, the said damper plate member 50 has itsperipheral surface that is formed at its lower side with a saiddownwards tapered surface 53 progressively reduced in diameter downwardsand at its upper side with a said upwards tapered surface 54progressively reduced in diameter upwards.

A damper receiving member 55, that is cup shaped, is disposed on abottom surface of the said vessel 40 and has at its central portion aguide rod 56 projecting upwards therefrom, that is adapted to beslidably fitted in the above mentioned guide bore 51 coaxiallytherewith. And, the said guide rod 56 has a diameter that is smallerthan by a small length S such that when the said guide bore 51 isaxially displaced relative to to the said guide rod 56, the said dampingliquid 60 can be freely passed into and out of the said guide bore 51through an interstice that is defined by the length S. Between the saiddamper receiving member 55 and the said damper plate member 50 there isinterposed the said spring member 57, which is here comprised of a pairof coil springs 58a and 58b having different spring constants.

The lower surface of the said damper receiving member 55 has a sphericalsurface that is substantially the same as the spherical surface of theinner bottom surface of the said vessel 40 so that it may be slidabletransversely to the vertical axis. Also, the upper portion of the saiddamper receiving member 55 has an inner surface that is substantially inparallel with and opposing to the downwards tapered surface 53 of thesaid damper plate member 50 across a predetermined spacing.

On the other hand, a said rubber stopper 59, which is provided with asaid tapered recess 59a, is disposed below a said base plate 47 of theabove mentioned rubber mount 43 so that when the said damper platemember 50 is moved upwards more than a predetermined distance, the saidupwards tapered surface 54 may contact with an inner surface of the saidrecess 59a and may thus no longer be moved upwards.

In the construction mentioned above, the said mounted body will besupported on the said frame side via the said liquid sealed suspensionunit C.

And, if the said mounted member is then stationary, its weight is actingas an initial load on the said liquid sealed suspension unit C. Thisstate is the state shown in FIG. 13. The vertical load that thendevelops will be supported only by that 58a of the said coil springswhich has a larger spring constant of the said spring member 57.

When the said mounted member is vertically vibrated, the said guideshaft 42 will be axially vibrated. In the state in which it has beendisplaced from the state in which it received the above mentionedinitial load, the vertical load will be resiliently supported by thesaid pair of coil springs 58a and 58b of the said spring member 57. And,if this vertical vibration is increased or the weight of the saidmounted member is enlarged so that the said guide shaft 42 may be moveddownwards against the said spring member 57 from the state shown in FIG.13, the lower surface of the said attachment bracket 48, as shown inFIG. 14A, will come to contact with the upper surface of the saidcylindrical member 45a inside of the said rubber mount 43 and thereafterthe vertical load will be supported by the said spring member 57 as wellas a stress that is created by the deformation in the shearing directionof the said rubber mount 43. Then, the load will be resilientlysupported by the laminated rubber layers of the said rubber mount 43 andthe said pair of coil springs 58a and 58b.

And, when a maximum load is acting downwards, the lower surface of thesaid attachment bracket 48 will contact with the upper surface of thesaid rubber layer 46d that is located at the outermost side of the saidrubber mount 43 and the said rubber layer 46d will serve as a stopper,thereby bringing about a stroke end.

Since the laminated rubber layers of the above mentioned rubber mount 43become structurally softer as they go inside thereof, the springcharacteristic of the said rubber mount 43 will be the characteristicthat it becomes more rigid (the spring constant increased) as thevibration amplitude is increased.

Also, according to the construction mentioned above, in a state in whichthere is no load, as shown in FIG. 14B the said guide shaft 42 will bethrusted upwards by one spring coil 58a so that the upward taperedsurface 54 of the said damper plate member 50 may contact with the innersurface of the said recess 59a, thus bringing about a stroke end.

Also, as shown in FIGS. 14A and 14B, in the vibratory operation of theabove mentioned liquid sealed suspension unit C, it can be seen that,with the said guide shaft 42 moved up and down the said damper platemember 50 is moved up and down in the said damper receiving member 55,the said damping liquid 60 within the said damper receiving member 55will be displaced through the gap between the downwards tapered surface53 of the said damper plate member 50 and the inner surface of the saiddamper receiving member 55 and, as a consequence, a damping force willbe created by the fluid resistance that is then produced.

Also, when the above mentioned operation is effected, a similar dampingforce will be created between the upwards tapered surface 54 of the saiddamping plate member 50 and the inner surface of the recess 59a of thesaid rubber stopper 59.

FIG. 19 is a graph showing the relationship of the displacement of thesaid damping plate member 50 with respect to the load that is effectiveduring the up and down damping action thereof mentioned above. In thegraph, the solid line represents a static spring characteristic due tothe elastic deflections of the the said spring member 57 and the saidrubber mount 43 whereas the one dot chain line represents a dynamicspring characteristic due to the above mentioned elastic deflections towhich the damping characteristic by the said damping liquid 60 is added.In this connection it should be noted that the said dampingcharacteristic due to the said damping liquid 60 became effective if therate of operation of the said damper plate member 50 was 0.2 m/sec.

In the said static spring characteristic curve shown in FIG. 19, thecharacters a, b and c correspond to the supporting state by the saidcoil spring 58 alone, the supporting state by both the said springs 58aand 58b and the state in which an elastic support by the said rubbermount 43 is added when the upper end of the said innermost cylindricalmember 45a makes a contact with the said attachment bracket 48,respectively.

And, in the above mentioned elastic support state by the rubber mount43, it is seen that the state c changes to provide the dynamic springcharacteristic curve when the vibration produced damping characteristicis added to that of the said damper plate member 50 itself.

In this way, in the upward and downward movements of the said guideshaft 42, it can be seen that when it is moved downwards (in theretracted part of a vibration), the load will be supported by the saidpair of coil springs 58a and 58b; and, when it is further moveddownwards, the load will be supported by the said pair of coil springs58a and 58b as well as by the said laminated rubber layers 46a, 46b, 46cand 46d of the rubber mount 43 when the said cylindrical member 45athereof makes a contact with the said attachment bracket 48. Then, asmentioned previously, the damping action by the said damping liquid 60,that is produced by the vibrations, will be added. It should also benoted here that with the laminated rubber layers 46a, 46b and 46c beingstructurally softer as they go inside, the spring characteristic willthen be the characteristic that the rigidity is increased (the springconstant increased) as the distance of displacement of the said guideshaft 42 is increased.

On the other hand, when the said guide shaft 42 is moved upwards (in theextended part of a vibration), it can be seen that while the springcharacteristic will be softer (the spring constant reduced) as thedistance of displacement of the said guide shaft 42 is increased, thesaid damper plate member 50 acting as a liquid stopper will cause thedamping effect to be increased as the said distance of displacement isincreased. Accordingly, because of the fact the force of resistance isprogressively increased as the said distance of displacement increases,a damping characteristic of the vibrations will result without such animpact as accompanied by a bottom striking feeling.

Next, an explanation will be given with respect to the case in which atransverse force is acting on the said guide shaft 42.

Firstly, for a small vibration amplitude in this case, a favorablevibration absorbing characteristic will be obtained by a soft rubberfunction that is developed by the innermost rubber layer 46a of the saidrubber mount 43.

On the other hand, if a large rolling is produced, as shown in FIGS. 15Aand 15B, the said guide shaft 42 will be largely inclined (FIG. 15A) orwill be displaced in parallel transversely (FIG. 15B). Then, the saidroll preventing stopper 49 will make a contact with the said cylindricalmember 45a to resiliently support the said drive shaft 42 in the rollingdirection. Also, the said guide bore 51 and the said guide rod 56 willthen be fitted with each other to allow the said guide shaft 42 to bedisplaced and at the same time to permit the damper receiving member 55to be displaced while being rubbed with the inner bottom surface of thesaid vessel 40. The rolling force will then be damped by the slidingfrictional force which then develops. Also, then, because while the saidguide shaft is being displaced, the said damper receiving member 55 isdisplaced via the said plate member 50 and the said guide rod 56transversely while thrusting aside the said damping liquid 60 inside ofthe said vessel 40, the rolling force will be damped also by the fluidresistance that is then developed.

In connection with the above, it should be noted in this construction,an elastic material 62 having a high flexibility may be disposed in thegap between the said damper receiving member 55 and the said vessel 40,as shown by the two dot chain line in FIG. 13.

FIG. 20 shows the relationship (transverse spring characteristic) of thetransverse displacement of the above mentioned guide shaft 42 withrespect to the weight of the said rubber mount 43 in a case where atransverse force is acting on the said guide shaft 42.

As the said guide shaft 42 is displaced transversely the said innermostrubber layer 46a, that is the softest, will first be deformed mainly inthe direction of its thickness to exhibit the spring characteristic d.Then, the range e represents a range before the said roll preventingstopper 49 comes in contact with the said cylindrical member 45a. Aswill be apparent from the spring characteristic d, with the said rollpreventing stopper 49 coming into contact with the said cylindricalmember 45a, the transverse load will be supported by both the saidstopper 49 and the said rubber layer 46a. Then, the springcharacteristic is a rigidity reduced a little (the spring constantincreased).

Next, mainly the intermediate rubber layer 46b following the saidinnermost rubber layer 46a will be deformed to exhibit the springcharacteristic f and then the outermost rubber layer 46c will mainly bedeformed to exhibit the spring characteristic g.

In this case, the said laminated rubber layers 46a, 46b and 46c willbecome softer as they go inside and will become more rigid as they gooutside so that the spring characteristic f, g of each range may bevaried linearly.

In contrast to the above, as shown in FIG. 16 (FIG. 12), by configuringthe said laminated rubber layers 46a and 46b in cross section so thattheir respective outer axial height may be greater than their inneraxial height to provide a substantially truncated conical cross sectionas well, the transverse spring characteristic of the said rubber mount43 can be rendered gradually more rigid with respect to its transversedeformation. In this connection it should be noted that in this case aswell the said inner rubber layer 46a is made softer than the said outerrubber layer 46b.

The transverse spring characteristic in this case is shown in FIG. 21.More specifically, the character h in FIG. 21 represents the springcharacteristic in the state in which the said innermost rubber layer 46is mainly deformed and the character i therein represents the springcharacteristic in the state in which the said outer rubber layer 46b ismainly deformed. And, the dotted line in the Figure represents the casein which the cross sectional configuration of the both rubber layers 46aand 46b is of a substantially trapezoidal cross section as shown in FIG.16, and is a smooth curve. Also, the solid line in the Figure representsthe case in which the cross section of the innermost rubber layer 46ahas its inner side axial length and its outer side axial length whichare substantially identical to each other as shown in FIGS. 5 and 9whereas the cross section of the outer rubber layer 46b is asubstantially trapezoid as shown in FIG. 16 and in which the springcharacteristic h is varied linearly whereas the spring characteristic iis a smooth curve. In the Figure, the range j corresponds to the statebefore the said roll preventing stopper 49 comes in contact with thesaid cylindrical member 45a.

The guide bore 51 of the said damper plate member 50 and the guide rodof the said damper receiving member 55 are fitted with each other with agap formed between them, as mentioned previously. Thus, the gap of aspacing S/2 in the diametric direction is formed at a portion where thesaid guide bore 51 and the said guide rod 56 are fitted with each other.When the said damper plate member 50 is axially vibrated, the saiddamping liquid 60 introduced into the said guide bore 51 can be freelypassed out of and into it through the said gap. Accordingly, with thesaid damping liquid sealed between the said guide hole 51 and the saidguide rod 56, there will be nothing to prevent the required dampingcharacteristic.

Also, according to this construction, it can be seen that if atransverse force is acting on the said damper plate member 50 to vibratethe said guide shaft transversely the vibrations with an amplitude thatis lower than a backlash between the said guide 51 and the said guiderod 56 will be absorbed by the said rubber mount alone since the saiddamper receiving member 55 is not displaced transversely. And, ifvibrations are produced with an amplitude that exceeds the abovementioned backlash, the said damper receiving member 55 will bedisplaced transversely. Since an abutting frictional force is thenproduced between the said damper receiving member 55 and the innerbottom surface of the said vessel 40 and serves as a frictional dampingforce, an enlarged damping force will be generated.

It can thus be seen that this allows a vehicle to be comfortable to ridein even as in a case where it is traveling on such as a graveled roadfor the purpose of leveling the ground to produce high frequencyvibration with a small transverse amplitude.

FIGS. 17A and 17B show other examples which are different as to theconfiguration in which the guide bore of the said damper plate member 50and the guide rod of the said damper reception member 55 are fitted witheach other. What is shown in FIG. 17 has a construction in which a guiderod 56a which is substantially circular in cross section but of which aportion on its outer surface is chamfered is fitted in the said guidebore 51 that is circular in cross section, with a small intersticebetween them and with a gap 56b that is arcuate in cross section, whichserves to prevent the said damping liquid 60 from being sealed in thespace in the said guide bore 51.

What is shown in FIG. 17B has a configuration in which a guide rod thatis hexagonal in cross section is fitted in the said guide bore that iscircular in cross section, with six minute interstices and with sixsmall gaps 56c each of which is arcuate in cross section and which serveto prevent the said damping liquid 60 from being sealed in the space inthe said guide bore 51.

According to these constructions, it can be seen that when a force isacting transversely on the said damper plate member 50, the said damperplate member 50 and the said damper receiving member 55 will be vibratedintegrally in a transverse direction. This will give rise to a goodresponse, thus allowing a vehicle to be comfortable to ride in where itis traveling on a not so much heavily bad road (such as an irregular orwavy road).

In the above mentioned third embodiment of the present invention, itshould also be noted that in a case where a frictional resistance of thesaid damper receiving member 55 for the inner bottom surface of thevessel is not expected as a vibration damping force, the said damperreceiving member 55 may be securely fixed to the vessel 40 by welding orthe like. In this case, it is necessary to enlarge the gap between thesaid guide rod 56 and the said guide bore 51.

Also, a soft, elastic material may be interposed between each springcoil 58a, 58b of the said spring member 57 and the damper plate member50.

Further, while in each of the above mentioned embodiments the damperreceiving member is provided, it should also be noted that the same maybe omitted and the said spring member 57 may be adapted to make a directcontact with the inner bottom surface of the said vessel 40. In thiscase, it can be seen that there is no damping effect due to thefrictional resistance between the said damper receiving member 55 andthe inner bottom surface of the said vessel 40.

Also, it should be noted in each of the above mentioned embodiments ofthe present invention, the laminated rubber layers 46a, 46b, 46c and 46dof the said rubber mount 43 were composed of chloroprene rubber having ahardness range between HS 50° and 65° so that they may be progressivelylowered in hardness from the outside to the inside. Also, the saiddamping liquid 60 was composed of a silicone oil having a viscosity of 5to 100000 cst and the said coil spring 58a, 58b was composed of astainless spring steel having a spring constant of 5 to 50 kg.f/mm. And,the above mentioned damping liquid 60 had added thereto a lubricatingagent such as nylon (trade name), polyacetal or polystyrene.

FIGS. 18A and 18B show, respectively, liquid sealed suspension units Dand E constituting a fourth and a fifth embodiment of the presentinvention. The liquid sealed suspension unit D shown in FIG. 18A andconstituting the fourth embodiment of the present embodiment makes useof a pair of coil springs 63a and 63b which constitute a said springmember 57, which are arranged vertically in series as divided and whichhave an identical direction of expansion and contraction. The said coilsprings 63a and 63b are interposed between a said guide shaft 42 and asaid damper plate member 50a and between the said damper plate member50a and a damper receiving member 55a, respectively.

And, the said vessel 40 has fastened thereto a stopper 90 for regulatingthe displacement of the said damper plate member 50a towards the side ofthe said guide shaft 42.

In this case, the lower coil spring 63b has a spring constant k₂ that isgreater than a spring constant k₁ of the upper coil spring 63a. Bypreliminarily applying an initial load to the said lower coil spring63b, a spring force having the upper spring constant k₁ is effective upto a certain preset load and when the said preset load is exceeded, aspring force having a spring constant k that is expressed by k=1/(1/k₁+1/k₂) will become effective.

The liquid sealed suspension unit E shown in FIG. 18B constituting thefifth embodiment of the present embodiment makes use of a pair of coilsprings 64a and 64b which constitute a said spring member 57, which arearranged vertically in series as divided and which have oppositedirections of expansion and contraction. The said coil springs 64a and64b are interposed between the upper side of a said damper plate member50b and a said base plate 47a and between the lower side of the saiddamper plate member 50b and a damper receiving member 55b, respectively.

In the case of this example, in the state in which the downwarddisplacement of the said guide is short and the said upper coil spring64a is effective, the said lower coil spring 64b will be effective aswell, a spring force that is then effective having a spring constant:k=k₁ +k₂. In the state, however, in which the said upper coil spring 64ais left from the said base plate 47a and then fully expanded, a springforce that is then effective will have a spring constant which is equalto the spring constant k₂ of the said lower spring 64b.

FIGS. 22 and 23 show each a relationship between a displacement and aload that is effective to the spring member 58a, 58b when each of theabove mentioned fourth and fifth embodiments of the present invention isadopted, respectively.

FIG. 22 applies to the fourth embodiment shown in FIG. 18A. In theFigure, the character k represents the spring characteristic in thestate in which only a spring force having the upper spring constant k1is effective. Then, the said damper plate member 50a is held in contactwith the said stopper 90 at the side of the said vessel 40 by anattachment load of the said lower side spring 63a. The character mrepresents the spring characteristic in the state when a spring forcehaving the spring constant: k=1/(1/k₁ +1/k₂) by the said upper sidespring 63a and the said lower side spring 63b. The character nrepresents the spring characteristic in the state after the saidattachment bracket 48 has made a contact with the upper surface of therubber layer 46d (i. e. the rubber stopper) located at the outermostside of the said rubber mount 43.

This will render the spring characteristic in the load range of the cabmounted region (k) rigid and the spring characteristic in a load rangeof the vibration absorbing region (m) that exceeds the said load rangesoft. Thus, since there will, in the load range of the cab mountedregion (k), be developed no increase in the amount of displacement byvaried mounted loads produced when the spring characteristic is softenedin order to improve the vibration absorptivity, it will be possible toreduce a variation in the said amount of displacement with a pluralityof such liquid sealed suspension units in the said load range.

This can be explained in some more detail below.

The relationship between a displacement and a load corresponding to atarget range of the cab mounted state when the said single coil spring57 is used as in the first embodiment of the present invention shown inFIG. 5 is represented by the line o in FIG. 22. And, while the springcharacteristic with which the vibration absorbing region (m) may be setis required in order to improve the vibration absorptivity, in the caseof a similar spring characteristic shown by the line o, if there is adifference Q in the mounted load, it is seen that the amount ofdisplacement due to that will be increased to W and a variation in thesaid amount of displacement with a plurality of liquid sealed suspensionunits will then be increased. Thus, when the cab is supported with aplurality of liquid sealed suspension units, there will develop atendency for the cab not to be mounted horizontally. Also, for thisreason, when a given cab is exchanged with another cab having adifferent weight, an extreme vertical difference between them can takeplace so that the cab may even interfere with some other equipment.

However, since the forth embodiment shown in FIG. 18A enables the rangek shown in FIG. 22 to be set as the target range of the cab mountedstate, it also enables the amount of displacement V for the same mountedload difference Q to be limited as small. This, in turn, enables avariation in the said amount of displacement with a plurality of liquidsealed suspension units to be small. Thus, when a cab is supported witha plurality of liquid sealed suspension units, it can be made possibleto support the cab with no inclination thereof whatsoever. Also, for thesame reason, if a given cab is exchanged with another cab having adifferent weight, their vertical difference can be limited to be sosmall that it may no longer interfere with any other equipment.

FIG. 23 applies to the fifth embodiment shown in FIG. 18B, where thecharacter p represents the spring characteristic in the sate in whichboth the said upper coil spring 64a having the spring constant k₁ andthe said lower coil spring 64b having the spring constant k₂, that is,the state in which the spring constant: k=(k₁ +k₂) is effective. Thecharacter q represents the spring characteristic in the state in whichthe said upper coil spring 64a has departed from the said base plate 47aand only the said lower spring 64b is effective, that is, the state inwhich the spring force having the spring constant k₂ is effective. And,the character r represents the spring characteristic in the state afterthe said attachment bracket 48 has made a contact with the said rubberstopper 46d.

According to this construction, a similar operation and effect can beobtained to those in the fourth embodiment shown in FIG. 18A.

More specifically, the amount of displacement W' for the mounted loaddifference Q in an example using the single coil spring and shown by thecharacter s can be limited to the amount of displacement V'.

It should be noted at this point that compared with the springcharacteristic shown in FIG. 22 and corresponding to the fourthembodiment, the spring characteristic shown in FIG. 23 and correspondingto the fifth embodiment has an amount of displacement due to the mountedload difference reduced.

Also, with respect to the above mentioned liquid sealed suspension unitsC, D and E which represent the third, fourth and fifth embodiments,respectively, it should be noted that the liquid sealed suspension unitC using the parallel type spring 57 is desirably used in supporting acab of which the mounted load is small or which may not be exchangedwith another cab having a different weight, when mounted at a pluralityof sites. This type of the liquid sealed suspension unit C has a springmember hardened stepwise and thus is free from a feeling of discomfortsuch a bottom striking feeling. Also, it eliminates the need for anexternally equipped stopper and hence is simple in construction.

On the other hand, the liquid sealed suspension units D and E shown inFIGS. 18A and 18B, respectively, in which a pair of coil springs aredisposed vertically up and down are each desirably used in suspendingcabs of different mounted loads whose difference is large.

And, the liquid sealed suspension unit D is desirably used in suspendinga cab whose mounted load is light or a cab on a vehicle traveling forleveling the ground (or traveling on the graveled road) to produce asmall vibration amplitude, and may be provided with a damper platemember in the form of a flange at the lower end of the said guide shaft42a corresponding to the spring constant of the coil springs, Thus, itprovides a damping action that is well balanced with the damping actionby the spring member and that is finely adjusted for desired dampedresults.

Also, the liquid sealed suspension unit E is desirably used insuspending a cab whose mounted load is heavy or a cab on a vehicledesigned for a bad road to produce large vibration amplitude. Althoughits damping action by the damper plate member cannot be set to varylargely compared with the liquid sealed suspension unit D, it has theadvantage that its transverse damping effect is high.

While the present invention has hereinbefore been described with respectto certain illustrative embodiments thereof, it will readily beappreciated by a person skilled in the art to be obvious that manyalterations thereof, omissions therefrom and additions thereto can bemade without departing from the essence and the scope of the presentinvention. Accordingly, it should be understood that the presentinvention is not limited to the specific embodiments thereof set outabove, but includes all possible embodiments thereof that can be madewithin the scope with respect to the features specifically set forth inthe appended claims and encompasses all equivalents thereof.

What is claimed is:
 1. A liquid sealed suspension unit comprising:afirst member; a second member adapted to be fixed to a frame, said firstand second members being independent of each other; a cylindrical rubbermount which couples together said first and second members such thatsaid cylindrical rubber mount is secured to said first member and saidsecond member is mounted so as to be slidable in an axial directionthereof relative to said cylindrical rubber mount, said cylindricalrubber mount including a plurality of cylindrical rubber layerslaminated via a plurality of cylindrical members, with said cylindricalrubber layers having at least one of:different thicknesses in a radialdirection thereof, and different heights in an axial direction thereof;a vessel secured to said first member and including a liquid sealedchamber; a damping liquid sealed in said liquid sealed chamber; a damperplate member provided at one end of said second member and positionedwithin said liquid sealed chamber; and a spring member, including atleast one spring coil, interposed between said damper plate member andan inner bottom surface of said vessel.
 2. A liquid sealed suspensionunit, as set forth in claim 1, wherein the cylindrical rubber layers ofsaid cylindrical rubber mount are different in hardness in said radialdirection.
 3. A liquid sealed suspension unit, as set forth in claim 2,wherein said cylindrical rubber layers of said cylindrical rubber mounthave cross sectional configurations in which an outer one of saidcylindrical rubber layers is higher than an inner one of saidcylindrical rubber layers in said axial direction.
 4. A liquid sealedsuspension unit, as set forth in claim 2, further comprising:a sleevewhich retains a bearing that is fitted so as to be axially slidablerelative to said second member and to which said cylindrical rubbermount is fastened; and a roll preventing stopper mounted to an outsideof said sleeve so that said roll preventing stopper may be brought intoa loosely fitting state with an inner circumferential surface of aninner one of said cylindrical members that opposes said sleeve, with aninner one of said cylindrical rubber layers positioned between saidsleeve and said inner one of said cylindrical members.
 5. A liquidsealed suspension unit, as set forth in claim 2,further comprising astopper member disposed above said vessel; and wherein said dampingplate member has a peripheral surface which is formed with a downwardtapered surface and an upward tapered surface; said downward taperedsurface opposing an inner surface of said vessel; and said upwardtapered surface opposing an inner surface of said stopper member.
 6. Aliquid sealed suspension unit, as set forth in claim 2, wherein saidspring member comprises a plurality of coil springs.
 7. A liquid sealedsuspension unit, as set forth in claim 1, wherein said cylindricalrubber layers of said cylindrical rubber mount have cross sectionalconfigurations in which an outer one of said cylindrical rubber layersis higher than an inner one of said cylindrical rubber layers in saidaxial direction.
 8. A liquid sealed suspension unit, as set forth inclaim 7, further comprising:a sleeve which retains a bearing that isfitted so as to be axially slidable relative to said second member andto which said cylindrical rubber mount is fastened; and a rollpreventing stopper mounted to an outside of said sleeve so that saidroll preventing stopper may be brought into a loosely fitting state withan inner circumferential surface of an inner one of said cylindricalmembers that opposes said sleeve, with an inner one of said cylindricalrubber layers positioned between said sleeve and said inner one of saidcylindrical members.
 9. A liquid sealed suspension unit, as set forth inclaim 7,further comprising a stopper member disposed above said vessel;and wherein said damping plate member has a peripheral surface which isformed with a downward tapered surface and an upward tapered surface;said downward tapered surface opposing an inner surface of said vessel;and said upward tapered surface opposing an inner surface of saidstopper member.
 10. A liquid sealed suspension unit, as set forth inclaim 7, wherein said spring member comprises a plurality of coilsprings.
 11. A liquid sealed suspension unit, as set forth in claim 7,wherein said damping liquid comprises a silicone oil having incorporatedtherein an additive agent with a lubricity, and wherein said additiveagent is selected from the group consisting of NYLON (trade name),polyacetal and polystyrene.
 12. A liquid sealed suspension unit, as setforth in claim 1, further comprising:a sleeve which retains a bearingthat is fitted so as to be axially slidable relative to said secondmember and to which said cylindrical rubber mount is fastened; and aroll preventing stopper mounted to an outside of said sleeve so thatsaid roll preventing stopper may be brought into a loosely fitting statewith an inner circumferential surface of an inner one of saidcylindrical members that opposes said sleeve, with an inner one of saidcylindrical rubber layers positioned between said sleeve and said innerone of said cylindrical members.
 13. A liquid sealed suspension unit, asset forth in claim 1,further comprising a stopper member disposed abovesaid vessel; and wherein said damping plate member has a peripheralsurface which is formed with a downward tapered surface and an upwardtapered surface; said downward tapered surface opposing an inner surfaceof said vessel; and said upward tapered surface opposing an innersurface of said stopper member.
 14. A liquid sealed suspension unit, asset forth in claim 1, wherein said spring member comprises a pluralityof coil springs.
 15. A liquid sealed suspension unit, as set forth inclaim 1, wherein said damping liquid comprises a silicone oil havingincorporated therein an additive agent with a lubricity, and whereinsaid additive agent is selected from the group consisting of NYLON(trade name), polyacetal and polystyrene.
 16. A liquid sealed suspensionunit, as set forth in claim 2, wherein said damping liquid comprises asilicone oil having incorporated therein an additive agent with alubricity, and wherein said additive agent is selected from the groupconsisting of NYLON (trade name), polyacetal and polystyrene.
 17. Aliquid sealed suspension unit, as set forth in claim 1, furthercomprising:a damper receiving member positioned in said liquid sealedchamber so as to be slidable along an inner bottom surface of saidvessel, said damper receiving member and said damper plate member beingfitted with each other so that said damper plate member is movable in anaxial direction relative to said damper receiving member; and whereinsaid damper receiving member is interposed between said spring memberand said inner bottom surface of said vessel.
 18. A liquid sealedsuspension unit, as set forth in claim 17, wherein one of said damperplate member and said damper receiving member is formed with a guidebore, and the other of said damper plate member and said damperreceiving member is provided with a guide rod which is slidably fittedin said guide bore with a diametrical interstice between them such thatsaid damping liquid may freely pass therethrough.
 19. A liquid sealedsuspension unit, as set forth in claim 17, wherein:one of said damperplate member and said damper receiving member is formed with a guidebore whereas the other of said damper plate member and said damperreceiving member is provided with a guide rod which is slidably fittedwithout backlash in said guide bore; and one of said guide bore andguide rod has a cross sectional configuration which is different fromthat of the other of them so that an interstice is formed between theinner surface of said guide bore and an outer surface of said guide rodsuch that said damping liquid may freely pass therethrough.
 20. A liquidsealed suspension unit, as set forth in claim 17, further comprising astopper member disposed above said vessel; andwherein said damping platemember has a peripheral surface which is formed with a downward taperedsurface and an upward tapered surface; said downward tapered surfaceopposing an inner surface of said vessel; and said upward taperedsurface opposing an inner surface of said stopper member.
 21. A liquidsealed suspension unit, as set forth in claim 17, wherein said springmember comprises a plurality of coil springs.
 22. A liquid sealedsuspension unit comprising:a first member; a second member adapted to befixed to a frame, said first and second members being independent ofeach other; a cylindrical rubber mount which couples together said firstand second members such that said cylindrical rubber mount is secured tosaid first member and said second member is mounted so as to be slidablein an axial direction thereof relative to said cylindrical rubber mount,said cylindrical rubber mount including a plurality of cylindricalrubber layers laminated via a plurality of cylindrical members, withsaid cylindrical rubber layers having at least one of:differentthicknesses in a radial direction thereof, and different heights in anaxial direction thereof; a vessel secured to said first member andincluding a liquid sealed chamber; a damping liquid sealed in saidliquid sealed chamber; a damper plate member provided at one end of saidsecond member and positioned within said liquid sealed chamber; and aspring member, including at least one spring coil, interposed betweensaid damper plate member and an inner bottom surface of said vessel;wherein said cylindrical rubber layers of said cylindrical rubber mounthave cross sectional configurations in which an outer one of saidcylindrical rubber layers is higher than an inner one of saidcylindrical rubber layers in said axial direction.
 23. A liquid sealedsuspension unit, as set forth in claim 22, further comprising:a sleevewhich retains a bearing that is fitted so as to be axially slidablerelative to said second member and to which said cylindrical rubbermount is fastened; and a roll preventing stopper mounted to an outsideof said sleeve so that said roll preventing stopper may be brought intoa loosely fitting state with an inner circumferential surface of aninner one of said cylindrical members that opposes said sleeve, with aninner one of said cylindrical rubber layers positioned between saidsleeve and said inner one of said cylindrical members.
 24. A liquidsealed suspension unit, as set forth in claim 22further comprising astopper member disposed above said vessel; and wherein said dampingplate member has a peripheral surface which is formed with a downwardtapered surface and an upward tapered surface; said downward taperedsurface opposing an inner surface of said vessel; and said upwardtapered surface opposing an inner surface of said stopper member.
 25. Aliquid sealed suspension unit, as set forth in claim 22, wherein saidspring member comprises a plurality of coil springs.
 26. A liquid sealedsuspension unit, as set forth in claim 22, wherein said damping liquidcomprises a silicone oil having incorporated therein an additive agentwith a lubricity, and wherein said additive agent is selected from thegroup consisting of NYLON (trade name), polyacetal and polystyrene. 27.A liquid sealed suspension unit comprising:a first member; a secondmember adapted to be fixed to a frame, said first and second membersbeing independent of each other; a cylindrical rubber mount whichcouples together said first and second members such that saidcylindrical rubber mount is secured to said first member and said secondmember is mounted so as to be slidable in an axial direction thereofrelative to said cylindrical rubber mount, said cylindrical rubber mountincluding a plurality of cylindrical rubber layers laminated via aplurality of cylindrical members, with said cylindrical rubber layershaving at least one of:different thicknesses in a radial directionthereof, and different heights in an axial direction thereof; a vesselsecured to said first member and including a liquid sealed chamber; adamping liquid sealed in said liquid sealed chamber; a damper platemember provided at one end of said second member and positioned withinsaid liquid sealed chamber; and a spring member, including at least onespring coil, interposed between said damper plate member and an innerbottom surface of said vessel; wherein the cylindrical rubber layers ofsaid cylindrical rubber mount are different in hardness in said radialdirection; and wherein said cylindrical rubber layers of saidcylindrical rubber mount have cross sectional configurations in which anouter one of said cylindrical rubber layers is higher than an inner oneof said cylindrical rubber layers in said axial direction.
 28. A liquidsealed suspension unit comprising:a first member; a second memberadapted to be fixed to a frame, said first and second members beingindependent of each other; a cylindrical rubber mount which couplestogether said first and second members such that said cylindrical rubbermount is secured to said first member and said second member is mountedso as to be slidable in an axial direction thereof relative to saidcylindrical rubber mount, said cylindrical rubber mount including aplurality of cylindrical rubber layers laminated via a plurality ofcylindrical members, with said cylindrical rubber layers having at leastone of:different thicknesses in a radial direction thereof, anddifferent heights in an axial direction thereof; a vessel secured tosaid first member and including a liquid sealed chamber; a dampingliquid sealed in said liquid sealed chamber; a damper plate memberprovided at one end of said second member and positioned within saidliquid sealed chamber; a spring member, including at least one springcoil, interposed between said damper plate member and an inner bottomsurface of said vessel; a sleeve which retains a bearing that is fittedso as to be axially slidable relative to said second member and to whichsaid cylindrical rubber mount is fastened; and a roll preventing stoppermounted to an outside of said sleeve so that said roll preventingstopper may be brought into a loosely fitting state with an innercircumferential surface of an inner one of said cylindrical members thatopposes said sleeve, with an inner one of said cylindrical rubber layerspositioned between said sleeve and said one of said inner cylindricalmembers.
 29. A liquid sealed suspension unit comprising:a first member;a second member adapted to be fixed to a frame, said first and secondmembers being independent of each other; a cylindrical rubber mountwhich couples together said first and second members such that saidcylindrical rubber mount is secured to said first member and said secondmember is mounted so as to be slidable in an axial direction thereofrelative to said cylindrical rubber mount, said cylindrical rubber mountincluding a plurality of cylindrical rubber layers laminated via aplurality of cylindrical members, with said cylindrical rubber layershaving at least one of:different thicknesses in a radial directionthereof, and different heights in an axial direction thereof; a vesselsecured to said first member and including a liquid sealed chamber; adamping liquid sealed in said liquid sealed chamber; a damper platemember provided at one end of said second member and positioned withinsaid liquid sealed chamber; a spring member, including at least onespring coil, interposed between said damper plate member and an innerbottom surface of said vessel; a sleeve which retains a bearing that isfitted so as to be axially slidable relative to said second member andto which said cylindrical rubber mount is fastened; and a rollpreventing stopper mounted to an outside of said sleeve so that saidroll preventing stopper may be brought into a loosely fitting state withan inner circumferential surface of an inner one of said cylindricalmembers that opposes said sleeve, with an inner one of said cylindricalrubber layers positioned between said sleeve and said inner one of saidcylindrical members; wherein the cylindrical rubber layers of saidcylindrical rubber mount are different in hardness in said radialdirection.
 30. A liquid sealed suspension unit comprising:a firstmember; a second member adapted to be fixed to a frame, said first andsecond members being independent of each other; a cylindrical rubbermount which couples together said first and second members such thatsaid cylindrical rubber mount is secured to said first member and saidsecond member is mounted so as to be slidable in an axial directionthereof relative to said cylindrical rubber mount, said cylindricalrubber mount including a plurality of cylindrical rubber layerslaminated via a plurality of cylindrical members, with said cylindricalrubber layers having at least one of:different thicknesses in a radialdirection thereof, and different heights in an axial direction thereof;a vessel secured to said first member and including a liquid sealedchamber; a damping liquid sealed in said liquid sealed chamber; a damperplate member provided at one end of said second member and positionedwithin said liquid sealed chamber; a spring member, including at leastone spring coil, interposed between said damper plate member and aninner bottom surface of said vessel; and a stopper member disposed abovesaid vessel; wherein said damping plate member has a peripheral surfacewhich is formed with a downward tapered surface and an upward taperedsurface; said downward tapered surface opposing an inner surface of saidvessel; and said upward tapered surface opposing an inner surface ofsaid stopper member.
 31. A liquid sealed suspension unit comprising:afirst member; a second member adapted to be fixed to a frame, said firstand second members being independent of each other; a cylindrical rubbermount which couples together said first and second members such thatsaid cylindrical rubber mount is secured to said first member and saidsecond member is mounted so as to be slidable in an axial directionthereof relative to said cylindrical rubber mount, said cylindricalrubber mount including a plurality of cylindrical rubber layerslaminated via a plurality of cylindrical members, with said cylindricalrubber layers having at least one of:different thicknesses in a radialdirection thereof, and different heights in an axial direction thereof;a vessel secured to said first member and including a liquid sealedchamber; a damping liquid sealed in said liquid sealed chamber; a damperplate member provided at one end of said second member and positionedwithin said liquid sealed chamber; a spring member, including at leastone spring coil, interposed between said damper plate member and aninner bottom surface of said vessel; and a stopper member disposed abovesaid vessel; wherein said damping plate member has a peripheral surfacewhich is formed with a downward tapered surface and an upward taperedsurface; said downward tapered surface opposing an inner surface of saidvessel; and said upward tapered surface opposing an inner surface ofsaid stopper member; and wherein the cylindrical rubber layers of saidcylindrical rubber mount are different in hardness in said radialdirection.